Gaining an understanding of the mechanisms of pattern formation is the major objective of this investigation. The specific aim is to analyze the arrangement of structures in the cell surface region of a ciliate, Tetrahymena thermophila. Previous studies of hereditary reversals of asymmetry in the arrangement of cell-surface structures led to formulation and testing of a detailed "cylindrical coordinate model" (CCM) for organization of the ciliate cortex. This model, which is related to the "polar coordinate model" of French, Bryant, and Bryant, extends concepts of positional information to the intracellular level. The proposed work is intended to test this model further, and especially to extend its application to the molecular level. The major specific goal is to find proteins that are restricted to particular locations (rather than to specific structures) within the cell. The principal method will be the production of monoclonal antibodies raised against preparations of the surface layers and screened with gently fixed cells using indirect immunofluorescence. Some of the position-specific antibodies should fail to react with pattern mutants, such as the mirror- image janus mutants in which, according to the CCM, dorsal positional values are missing and are replaced by ventral values in reverse order. A second approach will be to use two-dimensional polyacrylamide gel electrophoresis to detect cell-surface proteins that are absent in janus mutants, and thus might respond to or conceivably embody positional information. Concurrent genetic studies will involve a continuing search for new mutations of the janus and related classes, and a further analysis of the onset and termination of expression of existing mutations following controlled mass matings. While these studies on Tetrahymena have no immediate relationship to human health, they are concerned with the general problem of developmental fields which is common to all complex organisms, including humans. J. M. Opitz, Editor of the American Journal of Medical Genetics, has pointed out that most congenital human malformations are defects in developmental fields in which, "...though the causes are many, final developmental paths...are few indeed" (Opitz, 1985, Amer. J. Med. Genet. 21, 1-11). The proposed research is concerned with understanding general rules that constrain "final developmental paths".